Generators having a rotor with permanent magnets are known. They are generally deemed to be reliable and require less maintenance than other generator topologies.
Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. Said rotation is normally transmitted through a rotor shaft to a generator, either directly or through the use of a gearbox. This way, the generator can produce electricity which can be supplied to the electrical grid.
Particularly for offshore wind turbines, direct drive systems employing permanent magnets are usually chosen. Such a direct drive wind turbine generator may have e.g. a diameter of 6-8 meters and a length of e.g. 2-3 meters. Hundreds of magnets may need to be attached, e.g. by screwing or gluing, to the circumference of the rotor. This manufacturing process can be cumbersome.
This size and type of generator is not limited to offshore applications and not even to the field of wind turbines only. Generators of considerable dimensions may also be found e.g. in steam turbines and water turbines.
Examples of permanent magnet rotors that aim at dealing with the aforementioned problem of the attachment of a large number of magnets may comprise a rotor rim and a plurality of permanent magnet modules arranged on the outer or inner circumference of the rotor rim.
A permanent magnet module may be defined as a unit having a plurality of permanent magnets, such that the plurality of magnets can be mounted and unmounted together. Such a module may have a module base with a shape suitable for housing a plurality of permanent magnets. The magnets may be fixed to the base in a diversity of manners. The base may be configured to be fixed to a rotor rim in such a way that the plurality of magnets are fixed together to the rotor rim through the module base. The use of permanent magnet modules may facilitate the manufacturing of a generator rotor.
Permanent magnets may be fixed to the module base mechanically by using e.g. wedges, and/or welding, and/or screwing, etc. Regardless of the attachment method chosen, such attachments preferably should be easy to make, in a relatively cheap manner, and the attachments should be able to withstand all relevant loads and do not affect the magnetic field in a negative manner.
The present disclosure aims at improving the prior art methods of manufacturing permanent magnet modules and the prior art permanent magnet modules.